Two-part local shoulder coil, and magnetic resonance tomography apparatus and method employing same

ABSTRACT

Improved patient comfort is provided by a symmetric local coil arrangement designed to support the production of an MRT image of a shoulder, wherein the housing of the local coil arrangement is composed of two separable parts. The symmetric local shoulder coil arrangement is designed to be useable for either of a right or left shoulder of a human subject by rotating the local coil arrangement about a rotational axis that is parallel to an axis of symmetry of the local shoulder coil and perpendicular to anterior and posterior members of the shoulder coil.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 12/770,901, filed Apr. 30, 2010, the entire contents of which is hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention concerns a local coil for acquiring magnetic resonance (MR) data from a shoulder of a patient, an MR apparatus and a method for use of a shoulder coil.

2. Description of the Prior Art

Magnetic resonance tomography (MRT), also called magnetic resonance imaging (MRI), is known e.g. from DE10314215B4.

Modern magnetic resonance systems normally operate with a number of various RF antennas (called coils in the following) for transmission and reception of radio-frequency pulses for exciting nuclei so as to emit magnetic resonance signals and/or for acquisition of the induced magnetic resonance signals. A magnetic resonance system normally has a large whole-body coil (body coil) permanently installed in the magnetic resonance scanner. The whole-body coil is typically arranged cylindrically (for example with a structure known as a birdcage structure) around the patient acquisition chamber in which the patient is supported on a bed (often also called a patient positioning table) during the measurement.

For increasing the signal to noise ratio (SNR) in magnetic resonance imaging, most MRI scanners today use local coils. Local coils are receiving antennas, which are brought close to the region that shall be imaged. For many parts of the body, dedicated coils exist (e.g. shoulder coil, wrist coil, head coil, spine coil, invasive coils e.g. for prostate imaging, etc.). For imaging of a shoulder, today's MRI systems provide a dedicated shoulder coil. Because of economic reasons (cost, scan time, workflow) it is desirable for the local coil to be easily placed on the patient. At the same time, the coil shall be comfortable for the patient. An MRI coil usually consists of a mechanical housing, which houses the antennas (mostly loop or butterfly antennas) and the active electronics which usually consist of a low noise amplifier and tuning/detuning circuits for the antenna.

Conventional shoulder arrays have the shape of a shell e.g. according to FIGS. 2 a and 2 b. In order to allow the coil to be as close as possible to the imaged volume, different sizes of coils have been built, to account for the different anatomy (shoulder size) of the patient population. Another topic which has to be addressed is the fact that the coil shall be applicable to the left and to the right shoulder. Today this is done by “rotating” the coil 180° along the z-direction (z is parallel to the main magnetic field BO). One disadvantage of today's shoulder array design is the shell-like shape of the coil. This requires that after the patient has been placed on the table, either the patient has to move his/her shoulder into the coil or the coil has to be moved with respect to the patient. This is uncomfortable for the patient, it can be difficult especially for injured patients and is s time consuming step in the workflow. These are the major disadvantages of the shell-design of a shoulder coil.

SUMMARY OF THE INVENTION

An object of the invention is to improve positioning of a patient's shoulder in a shoulder coil.

According to one aspect the invention, the housing of the shoulder local coil arrangement has two (separate or separable) parts (which can be separated from each other).

According to a further aspect the invention an MRT includes a local coil arrangement designed to support the production of an MRT image of a shoulder, wherein the housing of the local coil arrangement is formed of two parts, wherein the distance of the parts is alterable.

A further aspect the invention an MRT is a method for producing an MRT image of a shoulder of a patient, wherein at least two parts of a local coil arrangement are positioned adjacent to the shoulder between them.

An improvement results in the mechanical and (partly) electrical design of a shoulder array made from an anterior and a posterior part and a mechanical construction that allows the coil to be adapted to various patient sizes and left and right shoulders while minimizing the number of components necessary for the coil. The minimization of the number of different components goes along with an optimization of the costs and improved workflow. The split design of the coil makes it obsolete for the patient to move into the coil with a sideward movement (x-direction, i.e. orthogonally to the y-direction and z-direction) or to move the coil sideward towards the patient. The patient can comfortably lie down on the SPP and when he/she is lying on the SPP, the SAP (shoulder anterior part) can be placed on top of the SPP. This improves patient comfort and workflow and therefore gives direct benefit for the customer.

In a preferred embodiment of the invention, the housing of the local coil arrangement is formed of at least three parts, of which only two are in use simultaneously.

In a further preferred embodiment of the invention, a first part (SPP=shoulder posterior part) is closer to the patient table on which the shoulder can be positioned, than a further part (SAP=shoulder anterior part).

In a further preferred embodiment of the invention, one part is connectable either to the patient table or to a base plate which itself is then connectable to or placed on the patient table.

In a further preferred embodiment of the invention, the first part and the further part are movable towards a patient to allow adjustment to the size of a shoulder of the patient.

In a further preferred embodiment of the invention, one part is available in at least two sizes, and this part can be exchanged by a part with a different size.

In a further preferred embodiment of the invention, there is a plane of symmetry in a shoulder coil, which plane allows use of the shoulder coil for a left shoulder as well as for a right shoulder of a patient.

In a further preferred embodiment of the invention, each part of the local coil has a coil antenna which can be connected via a connection to an image generation unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a magnetic resonance tomography system

FIGS. 2 a, 2 b show known shoulder coils.

FIGS. 3-6 respectively show different embodiments of the shoulder coils.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a magnetic resonance tomography (MRT) scanner (data acquisition unit) 1 has a basic field magnet 2 with a cylindrical tube 3 and a patient table 4 for moving a patient 5 into the cylindrical tube 3 of the MRT scanner 1. As is known the basic field magnet 2 has a body coil built therein or inserted therein. Local coils 6 or 7 can be used near an imaged volume of the body of the patient, e.g. a shoulder coil 7 for shoulder imaging.

FIG. 2 a shows known shoulder coils 7 a, 7 b that respectively can be positioned at the shoulder of a patient.

FIG. 2 b shows the basic components of a known shoulder coil schematically, with an upper part 7 c and a lower part 7 d connected by an inseparable connector 7 e.

FIGS. 3-6 show different embodiments of a shoulder coil. For a better understanding, the coils are shown very schematically, but of course they can have a roundish and soft surface design as the known design in FIG. 2 a has (but according an embodiment of the invention as a two-part shoulder array).

The invention described herein allows shoulder imaging that overcomes the major drawbacks of today's approaches shown in FIGS. 2 a, 2 b. The basis of the invention is to split the housing of the shoulder coil in an upper (posterior) part and a lower (anterior) part.

In the following, the parts are called SAP (shoulder anterior part) and SPP (shoulder posterior part). The lower part can be connected either to the patient table or to a base plate, which itself can be connected to or placed on the patient table.

There are three preferred different approaches how a shoulder coil, made from an anterior and a posterior part can be designed mechanically:

According to the cross sectional view in FIG. 3, the parts SAP and SPP of a shoulder coil 7 are movable along the y-direction (indicated by arrow “y”) to allow adjustment to the anatomy of a patient 5 on a table 4; one preferred solution is to have the anterior and the posterior part mechanically identical as in so that moving the shoulder coil parts from the right shoulder 8 to the left shoulder 9 allows using the SAP as the posterior part and the SPP as the anterior part.

According to the cross sectional views in FIGS. 4 a and 4 b, the parts SAP and SPP of a shoulder coil 7 are not movable in the y-direction (they can be connected in an adjacent position), but there are two different sizes (FIG. 4 a size and FIG. 4 b size) available for the upper part SAP (for the left and right upper part in FIGS. 4 a and 4 b), to allow adjustment to the anatomy of the patient 5.

The two upper parts SAP (for the left and right shoulder) in FIG. 4 b are smaller than the two upper parts SAP (for the left and right shoulder) in FIG. 4 a.

One possible derivative would be to allow the larger and the smaller part be used as the anterior part and the posterior part, just as required by the patient's anatomy, i.e. using the bigger part SAP in FIG. 4 a as the lower posterior part and using the smaller part SPP in FIG. 4 a as the upper anterior part.

The local coil parts SAP, SPP can be (separably) fixed to each other by engagement elements 18,19 that can also produce an electrical connection between the coil portions respectively contained in the coil parts SAP, SPP.

According to FIGS. 5 a and 5 b, to further improve the solution in FIGS. 4 a and 4 b an additional plane “a” of symmetry through each shoulder coil part SPP and SAP (shown for SPP as an example in FIG. 5 a in elevated view) allows the shoulder coil part SPP to be used for different patient sizes and for left and right shoulders while minimizing the number of parts necessary for the shoulder coil.

A base plate 15 carries a shoulder coil part SPP, which is moved from the position according to FIG. 5 b in the direction of the arrow “move” to the position in FIG. 5 c and rotated according to arrow “rotate” to the position in FIG. 5 d.

For example, a long groove 16 in the base plate 15 in which an element of the shoulder coil part SXP engages can support this movement and rotation.

The base plate 15 can be positioned on a patient table.

The additional plane “a” of symmetry added in the mechanics makes it also favorable to make the antenna design symmetrical and therefore does not only affect the mechanical construction but also can affect the electrical design.

FIG. 6 shows wired connections 10, 11 of antennas (not shown) in shoulder coil parts SPP and SAP, which respectively are connected to an interface box 12, that is connectable to a known MRI system for producing images based on e.g. detected local coil antenna signals. The outlines of SPP and SAP schematically illustrate respective housings of those components, and conductors C that form the shoulder coil antenna itself are schematically shown inside those housings.

Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventors to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of their contribution to the art. 

What is claimed is:
 1. A method for selectively acquiring magnetic resonance (MR) signals from either a right shoulder or a left shoulder of an examination subject using a single shoulder of an examination subject using a single shoulder coil arrangement, said method comprising: configuring a shoulder coil arrangement comprising, a unitary housing and radio frequency (RF) coil contained in said unitary housing, to have a first portion and a second portion that together form a recess between said first portion and said second portion that is shaped to receive a human shoulder; configuring said coil arrangement to make said first and second portions three-dimensionally diagonally symmetric with respect to a diagonal plane of symmetry of said housing; when acquiring MR signals from a left shoulder of a subject, placing said shoulder coil arrangement on the left shoulder with the left shoulder in said recess and with said first portion anterior said left shoulder and said second portion posterior said left shoulder; when acquiring MR signals from a right shoulder of a subject, placing said shoulder coil arrangement on the right shoulder with the right shoulder in said recess and with said first portion anterior said right shoulder and said second portion posterior said left shoulder; and selectively acquiring said MR signals from the left shoulder or the right shoulder, depending on which of the left or right shoulders said coil arrangement is currently placed, with said RF coil, and making said MR signals available as electrical signals at terminals of said RF coil.
 2. The method of claim 1, further comprising: when acquiring MR signals from a left shoulder of a subject, placing said shoulder coil in a first angular position with respect to the patient; and when acquiring MR signals from a right shoulder of a subject, placing said shoulder coil in a second angular position with respect to the patient, the second angular position being rotated 90-degrees from said first angular position about an axis parallel to said diagonal plane of symmetry and perpendicular to said first and second portions.
 3. The method of claim 1, wherein the first portion and second portion of the shoulder coil arrangement together further includes, an anterior member, a first side member connected and perpendicular to the anterior member, a second side member connected and perpendicular to each of the first side member and the anterior member, and a posterior member parallel to and spaced apart from the anterior member, and connected and perpendicular to each of the first and the second side members, the shoulder coil arrangement being symmetric about a plane of symmetry that (a) is perpendicular to each of the anterior and posterior members, and (b) substantially bisects the angle between the first and second side members
 4. The method of claim 1, wherein the first portion and second portion include releasable connectors for mechanical and electrically coupling the first portion to the second portion.
 5. The method of claim 1, wherein the local shoulder coil arrangement further includes a single base plate that has a transverse guide disposed therein in which the housing is slidably mounted, the transverse guide defining a direction of transverse movement.
 6. The method of claim 5, wherein the transverse guide is a transversely extending recess in the base plate.
 7. The method of claim 1, wherein the housing is configured to allow a subject having a shoulder located in the local shoulder coil to lie on a patient table, and wherein said first portion is configured to be located closer to the patient table and wherein said second portion is configured to be located farther from the patient table.
 8. The method of claim 7, wherein said first portion of said shoulder coil arrangement includes a detachable connection to the patient table.
 9. The method of claim 7, wherein the patient table includes a base plate thereon, and wherein the first portion of said shoulder coil arrangement is configured to be connectable to the base plate.
 10. The method of claim 4, wherein the first portion and the second portion are configured to be moved toward each other in order to connect the two parts with each other.
 11. The method of claim 4, wherein the releasable electrical and mechanical connectors include a first electrical connector configured to electrically connect a part of the local shoulder coil in one of the first and second portions to a magnetic resonance imaging system, and a second electrical connector configured to electrically connect a part of the local shoulder coil in the other of the first and second portions to the magnetic resonance imaging system.
 12. The method of claim 5, further comprising: moving the local shoulder coil arrangement in a transverse direction about the transverse guide, from a first end of said guide to an opposite end of said guide, the first and second ends of the guides corresponding to either of two locations at which a subject's left and right shoulders are to be located when acquiring magnetic resonance (MR) signals. 